Biomedical Engineering Reference
In-Depth Information
0.1 mm
Figure 4.5. Disc D5 implanted in the bone marrow site of a rabbit epiphysis.
microporosity. It is therefore not surprising that these products may show differ-
ent in vivo performances. For the BCP bioceramic to have osteogenic/osteoinduc-
tive properties, high percentage microporosity and macroporosity are required.
These data showed that higher osteogenic properties were observed with BCP
discs with lower density (produced at a lower sintering temperature). These re-
sults confi rm that microporosity promotes osteogenic/osteoinductive properties
in BCP bioceramics.
The properties of ceramic, such as composition, geometry, porosity, size and
microstructure, should be considered as critical parameters for bone induction.
These properties play a more important role in bone induction than in mechani-
cal stability [49].
Such osteogenic/osteoinductive properties for BCP ceramics can be
explained by the formation of microcrystals with Ca/P ratios similar to those of
the bone apatite crystals observed after implantation of MBCP. The abundance
of these crystals was directly related to the initial
-TCP/HA ratio in the BCP:
the higher the ratio the greater the abundance of the microcrystals associated
with the BCP crystals. Using high resolution TEM, the authors demonstrated
that the formation of these bone apatite-like microcrystals after implantation of
calcium phosphates (HA, BCP) was non-specifi c, that is, not related to implanta-
tion site (osseous or non-osseous sites), subject of implantation, or type of CaP
ceramics.
The coalescing interfacial zone of biological apatite and residual BCP ce-
ramic crystals (mostly HA), provides a scaffold for further bone-cell adhesion
and stem cell differentiation into osteogenic lines, and further bone ingrowth. The
bone repair or bone regeneration process involves dissolution of calcium phos-
phate crystals and then a precipitation of needle-like carbonate hydroxyapatite
β
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